首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   283081篇
  免费   1974篇
  国内免费   615篇
化学   128862篇
晶体学   3922篇
力学   14540篇
综合类   10篇
数学   45133篇
物理学   93203篇
  2020年   1502篇
  2019年   1674篇
  2018年   10752篇
  2017年   11656篇
  2016年   7358篇
  2015年   2902篇
  2014年   3482篇
  2013年   8597篇
  2012年   10422篇
  2011年   19493篇
  2010年   12402篇
  2009年   12469篇
  2008年   17328篇
  2007年   20691篇
  2006年   6799篇
  2005年   12504篇
  2004年   8849篇
  2003年   8306篇
  2002年   6205篇
  2001年   5951篇
  2000年   4612篇
  1999年   3384篇
  1998年   2833篇
  1997年   2679篇
  1996年   2679篇
  1995年   2555篇
  1994年   2486篇
  1993年   2364篇
  1992年   2593篇
  1991年   2556篇
  1990年   2495篇
  1989年   2430篇
  1988年   2425篇
  1987年   2409篇
  1986年   2316篇
  1985年   3018篇
  1984年   3091篇
  1983年   2668篇
  1982年   2816篇
  1981年   2637篇
  1980年   2612篇
  1979年   2796篇
  1978年   2844篇
  1977年   2689篇
  1976年   2786篇
  1975年   2646篇
  1974年   2601篇
  1973年   2841篇
  1972年   1800篇
  1971年   1488篇
排序方式: 共有10000条查询结果,搜索用时 328 毫秒
21.
22.
23.
24.
25.
We study the full counting statistics of transport electrons through a semiconductor two-level quantum dot with Rashba spin–orbit (SO) coupling, which acts as a nonabelian gauge field and thus induces the electron transition between two levels along with the spin flip. By means of the quantum master equation approach, shot noise and skewness are obtained at finite temperature with two-body Coulomb interaction. We particularly demonstrate the crucial effect of SO coupling on the super-Poissonian fluctuation of transport electrons, in terms of which the SO coupling can be probed by the zero-frequency cumulants. While the charge currents are not sensitive to the SO coupling.  相似文献   
26.
27.
We summarize the results of our recent work on Bäcklund transformations (BTs), particularly focusing on the relation between BTs and infinitesimal symmetries. We present a BT for an associated Degasperis–Procesi (aDP) equation and its superposition principle and investigate the solutions generated by applying this BT. Following our general methodology, we use the superposition principle of the BT to generate the infinitesimal symmetries of the aDP equation.  相似文献   
28.
Nanocomposites based on poly-N-vinylcaprolactam (PVC), characterized by different drying temperatures of aqueous PVC solution at 25°С (PVC25) and 40°С (PVC40), with titanium(IV) oxide nanoparticles (TONs) (η-phase (TP: TiO2 – x · mH2O) with a superstructure to the anatase structure and ordered solid solution with partial replacement of oxygen atoms in the η-phase with peroxo group O 2 2– (PP: TiO x (O2)2 – x · nH2O)) have been obtained for the first time and characterized by X-ray diffraction and IR spectroscopy. It is found that a common feature of TP/PVC and PP/PVC obtained by dry mixing and grinding is the decrease in the number of water molecules for TP and PP in the interlayer space of the structure and their attachment to the PVC amide groups; the differences are related to the specificity of PVC behavior in these systems: mechanodestruction of PVC in PP/PVC40 and different numbers of water molecules in PVC25 and PVC40.  相似文献   
29.
Mesoscopic modeling at the pore scale offers great promise in exploring the underlying structure transport performance of flow through porous media. The present work studies the fluid flow subjected to capillarity-induced resonance in porous media characterized by different porous structure and wettability. The effects of porosity and wettability on the displacement behavior of the fluid flow through porous media are discussed. The results are presented in the form of temporal evolution of percentage saturation and displacement of the fluid front through porous media. The present study reveals that the vibration in the form of acoustic excitation could be significant in the mobilization of fluid through the porous media. The dependence of displacement of the fluid on physicochemical parameters like wettability of the surface, frequency along with the porosity is analyzed. It was observed that the mean displacement of the fluid is more in the case of invading fluid with wetting phase where the driving force strength is not so dominant.  相似文献   
30.
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号